When communication is performed between one device and another, a communication identifier is used to identify the device at the communication destination and/or the device at the communication source.
In recent years, a technique in which when a device at the communication source communicates with a device at the communication destination, a temporarily used communication identifier, rather than a permanently used communication identifier, is used as the communication identifier of the device at the communication source in order to prevent the communication identifier of the device at the communication source from being identified by the device at the communication destination has been used.
This temporarily used communication identifier is called “pseudonymous-name communication identifier” while the permanently used communication identifier is called “real-name communication identifier”.
Examples of prior-art technique documents disclosing a communication method using a pseudonymous-name communication identifier like this include Non-patent document 1.
Non-patent document 1 discloses a technique to perform communication using an SIP (Session Initiation Protocol) by using GRUUs (Globally Routable User Agent URIs).
In the SIP, a real-name communication identifier called “SIP-URI” is used as a communication identifier. However, in the GRUU, there is a temporarily used communication identifier called “Temporary GRUU”.
This Temporary GRUU can be used as a pseudonymous-name communication identifier.
By using a Temporary GRUU, a device at the communication source, for example, can communicate with a device at the communication destination by using a Temporary GRUU indicating the device at the communication destination.
That is, even if the device at the communication source does not know the real-name communication identifier, which is SIP-URI, the device at the communication source can communicate with the device at the communication destination by using the pseudonymous-name communication identifier called “Temporary GRUU”.
Further, there are two types of pseudonymous-name identifiers, i.e., a pseudonymous-name communication identifier whose relation cannot be discriminated and a pseudonymous-name communication identifier whose relation can be discriminated.
The pseudonymous-name communication identifier whose relation cannot be discriminated means a communication identifier for which, when observed from the device at the communication destination, it cannot be determined that a plurality of pseudonymous-name communication identifiers indicate the same communication source device. For example, a pseudonymous-name communication identifier whose relation cannot be discriminated can be implemented by using a different pseudonymous-name communication identifier for each access to the same communication destination device.
Examples of its application include a case in which when a certain device at the communication source purchases a commodity in a certain Web site, a different pseudonymous-name communication identifier whose relation cannot be discriminated is used for each purchase of a commodity so that it is possible to prevent a commodity purchase history indicating what kinds of commodities the device at the communication source has purchased until now from being recorded.
That is, when the device at the communication source does not want its own commodity purchase history to be recorded, it may use a pseudonymous-name communication identifier whose relation cannot be discriminated.
In contrast to this, the pseudonymous-name communication identifier whose relation can be discriminated means a communication identifier for which, when observed from the device at the communication destination, it can be determined that a plurality of pseudonymous-name communication identifiers indicate the same communication source device.
For example, when a certain device at the communication source purchases a commodity in a certain Web site by using a pseudonymous-name communication identifier whose relation can be discriminated, it is possible to specify the device at the communication source that uses that pseudonymous-name communication identifier even if the same pseudonymous-name communication identifier is used for each purchase of a commodity.
Therefore, in the Web site, the preference of the device at the communication source can be analyzed by using the commodity purchase history from the device at the communication source, and recommendation of commodities that suit the preference of the device at the communication source can be made. Accordingly, the convenience of the Web site can be also improved for the device at the communication source.
That is, when the device at the communication source does not mind that its commodity purchase history is recorded and does want commodities that suit its preference to be recommended based on the commodity purchase history, it may use a pseudonymous-name communication identifier whose relation can be discriminated.
From these facts, whether the relation of a pseudonymous-name communication identifier should be able to be discriminated or not is preferably selected as appropriate for each communication.
[Non-patent Document 1]
J. Rosenberg “Obtaining and Using Globally Routable User Agent (UA) URIs (GRUU) in the Session Initiation Protocol (SIP)”, Internet Engineering Task Force Internet-Draft, draft-ietf-sip-gruu-15, Oct. 11, 2007, http://www.ietforg/internet-drafts/draft-ietf-sip-gruu-15.txt